Three people were missing after the explosion the cause of which is unknown, El Pais reports.
#URGENTE Aumenta a tres el número de muertos en la explosión de Zaragoza http://t.co/I2KLK9FXkm pic.twitter.com/KyTcI8fC0K
— La Gaceta (@gaceta_es) August 31, 2015
Firefighters, police and paramedics have arrived at the scene.
The blast at the factory was heard in the city.